Solve for $q$ : $18 = 23 + q$
Solution: Subtract $23$ from both sides: $ \begin{eqnarray} \\ \hphantom{18 {- 23}} &\hphantom{=}& \hphantom{q} \\ 18 &=& 23 + q \\ \\ {-23} && {-23} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ 18 {- 23} &=& q \\ \end{eqnarray} $ Simplify. $ q = -5$